Parallel-feeder protection.



PATENTED DEC. 25, 1906.

L. A. HAWKINS. PARALLEL FEEDER PROTECTION.

APPLICATION FILED MAY 21, 1904.

' INVE/ /TOR L a (HT/31706 Hawk/n s,

UNITED {STATES PATENT OEEIOE.

LAURENCE A. HAWKINS, OE S ENEOTADY, NEW YORK, ASSI'GNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PARALLEL-FEEDER PROTECTION.

, Patented Dec. 25, 1906.

Ap umi g filed May 21,1904; SerialN'o. 209,930.

for electrical transmission systems employing parallel feeders. In such systems, where a number of feeders are connected in parallel both at the generating and at the receiving end, as is customary, it is extremely desirable to provide automatic means for brealn'ng the circuit of a feeder at both ends when a fault occurs thereon. In case of a fault, such as a by interrupting the service.

ground or a short circuit, if a faulty feeder is cut out only at the generating end a faultcurrent will flow through the remaining feeders to the receiving end and back through the faulty feeder to the ground or short circuit. If simlen overload devices are relied upon for brea g the circuits ofthe feeders, a short-circuit on one feeder ma' result in opening the circuits of all the fee ers, there- In Order to avoid such interruption, it has been proposed heretofore to 'provlde discriminating devices, of the Watt-meter type provided with a potential-coil and a current-coil in series with a feeder. Such devices, however, fail in case of a serious, short-circuit, since the voltage on the potentialscoil may be lowered to a negligible amount. Furthermore, in the case of high-potential lines the expense is greatly increased by employing potential transformers for the rotective devices.

The object o my invention is to provide means for cutting out one of a number of parallel feeders whenever a fault occurs upon that feeder and whether the fault current is large or small. Furthermore, since no potential-transformers are employed in connection with my protective device my invention is particular y applicable to high-tension systems.

My invention will best be understood by reference to the accompanying drawings, in which Figure 1 shows diagrammatically an are rangement embed g my invention, and Fig. 2 shows a modification of the same.

In Fig. l G represents a generator or other source of energy connected to the station bus-bars 1 2. A B represent two feeders connected in parallel to bus-bar 1 through the circuit-breakers a ..'and b and through the rimary winding 0f ;-'a series transformer T.. The feeders of opp'plsite polarity I have indicated by a single f e '0, connected to a bus-bar 2. It will be understood, however, that the feeders of o posite polarity may form a duplication'of the eeders A and The receivmg ends of the feeders A and B are connected in parallel to the receiving bus-bar 4 through the series-transformer T and circuitbreaker cl and through the series transformer T and circuit-breaker d respectively. The feeders for the opposite polarity of the system are connected to the receiving bus-bar 3. vE

having two field-windings f and f connected to the secondaries of transformers T andT respectively, .and a movable e,which is connected across the secondary of trans' former T by means of the pilot-wire H and i winding e carries a movable switch-contact I, i which is normally held in the position shown by the centering-springs s' s and which when moved in either. direction closes a circuit from the battery or other source of current J through the tripping-coils of'one or the other of the circuit-breakers d and d. I j The operation is then as follows; The field-' coils f and f of relay E are so connected that they normally oppose each other and produce no flux in the stationary memberof the relay. The movable winding e is consequently-held in' its central position, asshown, by the-centeringisprings s s.- 'If, however,f one of the para e feeders, such as B, becomes grounded or short-circuite'd, itwill at once be disconnected from bus-bar 1 by the o ening of circuit-breaker Z). Current aso tend to flow from bus-bar -1 through' feeder A to the receiving end and back through feeder B to the fault. A reversalof current will consequently occur intran former '1 relative to the currentin transan earth connection. The core of movable represents a relay of the watt-meter type,

formers r and 'r'. The two field coilsfa'r'id f 2 will consequently assist each other' 1n pro member of relay E, and a movement'of A ing e will be produced. Swit'ch'coi1tact'I I current.

will closethe circuit of battery J through the tripping-coil of circuit-breaker d and will disconnect feeder B at its receiving end, thereby completely cutting it out of circuit. The circuit of feeder A is not broken, and the service is not interrupted. If, on the other hand, the feeder A is short-circuited, the phase of the flux in the stationary member of feeder B will be in opposition to its phase in the former case when feeder B was short-cir cuited. Consequently the direction of movement of movable winding e will be reversed, and circuit of battery J will be closed through the tripping-coil of circuit-breaker d. The relay E consequently is discriminating in its action and cuts out the faulty feed er without disturbing the circuit of the healthy feeder. Furthermore, it is always operative under all conditions, since it does not depend upon the potential of the system, but only upon the current in the two feeders and in their connection to the generating busbar, and these currents must always exist when a fault exists.

The form of discriminating device may be greatly varied and the connections of the pro: tective circuits reatly altered without varyingthe mode of operation. Thus in Fig. 2

the currents from the transformers T and T are used for tripping the circuit-breakers instead of employing an auxiliary source of Furthermore, the relay is omitted transformer secondaries are connected directly to the tripping-coil. The trip ing-coils t and t? are connected directly to t e secondaries oftransformers T and T while the tripping-coils t are connected -di rectly to the secondary of transformer T. The tri ping-coils are so wound or connected that t ey normally oppose each other. When the current in either feeder reverses, however, the currents in the tripping-coils of the circuit-breaker for that feeder will help each other and act to disconnect the circuit of the faulty feeder at the receiving end. Many other forms of discriminating devices may be employed for actuating the circuitbreakers Without departing from my invenand the tion, which consists in utilizing for securing the differential action the reversal of the current in a feeder relative to the current flowingfrom the source tothe feeders. Moreover, although I have shown my invention applied to a single-phase transmission system employi g only two parallel feeders it is evidently applicable to single or poly phase systems embodying any number of parallel feeders. Accordingly I aim in the appended claims to cover al such modifications. in the construction and arrangement of parts which do not depart from the spirit and scope of my invention. i

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In combination, a generating-station, a receiving-station, parallel feeders connecting said stations, series transformers at the receiving-station connected one in each feeder, a series transformer at the generating-station connected between said feeders and the source of energy, and. electroresponsive means at the receiving-station energized from said transformers and adapted and arranged to open the circuit of a feeder at its receiving end upon a reversal of current in said feeder relative to the current from the source of energ T to said feeders.

2. In combination, a generating-station, a receivi11g+,station, a plurality of feeders connected inparallel atone end to the source of energy and at the other end to the receiving apparatus, a series transformer at the gen crating-station having its primary connected between said feeders and the source of energy,

a second series transformer at the receivingstation having its primary in series with one of said feeders, and an electroresponsive means at the receiving-station connected to the secondary of both transformers and arranged to open the circuit of saidfeeder upon a reversal of current in said feeder relative'to' the current from the source of energy to said feeders.

3. In combination, a generating-station, a receiving-station, a plurality of feeders connected in parallel at one end to the source of energy and at the other end to the receiving apparatus, a series transformer having its primary connected between said feeders and the source of energy, and a device at the receiving-station connected to the secondary of said transformer and having a winding energized by the current in a feeder and responsive to a reversal of current in said feeder relative to the current in said secondary and arranged to open the circuit of said feeder at the receiving end.

4. In combination, a generating-station, a receiving-station, a plurality of feeders connected in parallel at one end to the source of energy and at the other end to the receiving apparatus, a series transformer at the generating-station having its primary connected between said feeders and the source of energy, a pilot-wire extending from the second- .ary of said transformer to the receiving end of said feeders, and a device at the receiving end connected to said pilotwire and having a winding energized by the current in a feeder and responsive to a reversal of current in said feeder relative to the current in said wire and arranged to ripen the circuit of said feeder at the receiving end.

5. In combination, a generating-station, a receiving-station, parallel. feeders connecting said stations, a winding at the generatingstation connected to be energized by the cur rent from the source of energy to said feeders, a second winding at the receiving-station coacting therewith and connected to be energized by the current in a feeder, and switch mg mechanism comprising an eleetrorespon'sive device at the receiving stetion controllby the -oint action of the icurrent in said windings and arrengedto open the circuit of the feeder at the receiving end upon a reversal of current therein relative to the current from the source of energy to the feeders,

6. in combination, a generating-station, e receiving-station, parallel feeders connecting said ste ens, a series transformer at the generating-station connected between said feeders end the source of energy, a. second series transformer at the receiving-station connected in the receiving end of a feeder, and an electroresponsive device at the receiving-- station connected to both transformers arranged to open the circuit or the feeder ripen a relative reversal of current in said trsns formers.

In witness whereof I have hereunto set my hand this 20th de of Me 1964.

' LAU EN0 1 A. F Witnesses:

' BENJAMIN B Home, HELEN Onronn: 

